Lockheed Martin's F-35 is a high-tech fighter jet with an even higher price tag. Photo: Lockheed Martin.

For all its troubles, Lockheed Martin's (LMT 0.73%) F-35 joint stealth fighter remains a very popular warplane -- both here and abroad.

Over the next 60 years, Lockheed Martin aims to sell as many as 5,100 F-35s to customers around the globe. And as we just learned from DoDBuzz, one single Pentagon contract could bring Lockheed 10% of the way toward scoring that goal.

What's the buzz?
In the course of last month's Paris Airshow, reports DoDBuzz, Lockheed revealed that it's currently negotiation with the U.S. Pentagon to win an order for 500 F-35 stealth fighter jets. This "block buy" of fighter jets would cover more planes than the Pentagon needs right now. In fact, it would stretch across three years' worth of orders, from 2018 through 2021.

To entice the Pentagon to buy all these planes at once, Lockheed hopes to offer the U.S. discounts of 10% or more on the planes' purchase price, discounts Lockheed will try to make possible by squeezing its own suppliers for price concessions of 10% on the parts they supply to Lockheed.

What's the cost?
If you ask Lockheed Martin, its F-35 stealth fighter isn't really all that an expensive plane to begin with. According to the company's website, a plain vanilla F-35A fighter jet costs only $98 million, while the F-35B hoverjet variant tips the scales at just $104 million, and an F-35C (designed to land on aircraft carriers) costs only a little bit more -- $116 million. All of these prices appear to be in the range given for competing top-of-the-line fourth-generation F/A-18 and F-15 fighter jets, for example, quoted at $92 million and $100 million a copy according to military tech website deagel.com.

Other sources, however, look at Congressional appropriations to buy the F-35, factor in the plane's development costs, the cost of outfitting the basic F-35 airframe with the electronic equipment that it needs to fly, plus supporting flight simulators and other tools and computers required to operate the plane, and come up with cost estimates of an entirely different magnitude -- as much as $337 million for the most expensive carrier variant.

The F-35 comes in three flavors: F-35A, F-35B, and F-35C. Photo: Lockheed Martin.

Military math
Be that as it may, let's give Lockheed Martin the benefit of the doubt and, for the time being at least, assume a generic "F-35" (a blend of the -A, -B, and -C variants) costs the Pentagon about $106 million today.

This suggests that in offering the Pentagon a discount, Lockheed hopes to lop about $11 million off that purchase price, cutting the F-35's cost to $95 million per unit. Times the 500 planes that they want to sell (460 for the U.S. military, plus an additional 40 planes destined for buyers in Canada and Denmark), that's $47.5 billion in new revenue that Lockheed is targeting.

Now consider that Lockheed Martin only brought in $45.1 million in revenue last year, from all the products it sold. This suggests that the F-35 contract, if concluded, would on its own make up 35% of Lockheed's business between 2018 and 2021. That's twice what the F-35 contributed to Lockheed's sales in 2014, and puts the company well on its way to getting half its business from the building of this one single warplane.

What it means to investors
For Lockheed Martin, the implications of this putative contract are obvious: First, a big influx of revenues for the defense contractor. And second, an even greater dependence on one single product for a rapidly growing slice of the company's revenue stream. In short, while winning the Pentagon's approval of a three-year block buy could be a good thing, it raises the risk that the F-35's oft-reported growing pains could cause Lockheed investors some pain of their own.

Caveat investor.

Sales of the Lockheed Martin F-35 could be about to take off -- and that could be a good thing or a bad thing. Photo: Lockheed Martin.